Helicopters of the type having turbine engines typically include turbine outlet temperature sensors and/or monitors to avoid “hot-starts”. It is well recognized that during the first few seconds of a start, the turbine outlet temperature will accelerate at a fairly rapid rate and should be closely monitored. For example, with respect to one type of engine, a pilot should abort the start if either a 927° C. maximum or 810° C. to 927° C. maximum ten second transient limitation is about to be exceeded.
A method for correcting a “hot-start” condition is disclosed in a U.S. patent of Morris et al. U.S. Pat. No. 5,101,619. As disclosed therein a method for correcting a “hot-start” condition in a gas turbine engine without requiring a complete shutdown and re-initiation of the startup sequence, includes temporarily interrupting the flow of fuel to the engine for a brief period of time following detection of an impending “hot-start” condition.
A further approach to avoid “hot-starts” is disclosed in a U.S. Pat. No. 6,357,219 of Dudd, Jr. et al. As disclosed therein, a turbine engine fuel delivery system has, a fuel bypass for diverting fuel exiting a fuel control away from the engine and back to the fuel pump to maintain a relatively constant pressure differential across the fuel control. A separate controllable flow fuel bypass is provided for selectively diverting fuel exiting the fuel control away from the engine and back to the fuel pump to decrease the rate of fuel flow to the engine and correct an over temperature condition. The fuel delivery system also includes an arrangement for enabling the controllable fuel bypass during engine startup and disabling the controllable fuel bypass when the engine reaches normal idle speed.
Pilot warning systems which provide a tactile warning to the pilot during flight operations are also known. For example, my earlier patent of Greene et al. U.S. Pat. No. 6,002,349 discloses a helicopter anti-torque limit warning device. As disclosed therein, the pilot warning system acts on foot pedals which are operatively connected to the controllable force mechanism. The pedal movement controls the amount of force exerted by the controllable force mechanism on the tail boom to control the orientation of the helicopter about the yaw axis. A position sensing device senses the location of at least one of the foot pedals between its first and second position, and a warning indicator operatively connected to the position sensing device provides a warning to the pilot when the sensed foot pedal reaches a predetermined distance from one of the first and second positions. The warning indicator provides a tactile warning such as vibration or shaking of the respective foot pedal to provide an unmistakable warning to the pilot that the foot pedal has reached a predetermined position near its maximum travel position.
Notwithstanding the above, it is presently believed that there is a present need and a large potential commercial market for an improved over stress warning system for avoiding “hot-starts” in accordance with the present invention. There should be a commercial market for such systems that provide an early warning to abort a start and thereby avoid serious damage to a turbine engine.
In addition, systems in accordance with the present invention provide an unmistakable tactile warning to avoid “hot-starts”. Further, systems in accordance with a preferred embodiment of the invention also include tactile warning means for avoiding over stressed conditions such as output temperature, torque and engine speed during flight operations. Such systems include a single multi-function tactile warning device for warning a pilot of dangerous conditions.